Brachiaria decumbens y fotosensibilización.

Evaluaciones de campo y laboratorio fueron realizadas en bovinos consumiendo Brachiaria decumbens bajo condiciones naturales y experimentales. En condiciones naturales se observaron signos de fotosensibilización, hemoglobinuria e ictericia, compatibles con daño hepático y disfunción renal. Experimentalmente se obtuvieron cambios detectables con laboratorio clínico, que indicaron marcada disfunción hepática y en menor grado renal. La histología bajo las dos condiciones de observación, mostró cambios de diversa intensidad de parénquima hepático y renal, e indicios de depresión en la hematopoyesis. Por los hallazgos descritos, Brachiaria decumbens fue hepatotóxico, con efectos clínicos y anatomopatológicos comparables a toxicidad, producida por la Brachiaria sp. (Tanner grass), Brachiaria brizantha y Tribulus terrestrisMaestría en CienciasMaestrí

Diagnóstico y alternativas de control al problema de la mortalidad bovina en un área del departamento del Vichada.

Se presenta un estudio que trata de identificar las posibles causas de la presencia de un síndrome que afecta generalmente a vacas paridas de ganado de carne, que se caracteriza en términos generales por: aislamiento del animal al apartarse de la manada, ataxia del tren anterior y, o del tren posterior, decúbito sin pérdida de apetito y posteriormente muerte, proceso que puede durar entre 7 y 25 días. El estudio se realizó en la altillanura del Vichada, entre noviembre de 1994 y octubre de 1995, período en el cual se recolectó información de 10 fincas, con muestreo de suelos de sabanas con bovinos en pastoreo, forrajes de sabana como oferta nutritiva y en 6 predios se tomaron muestras de sangre a terneros, novillas y vacas en época de verano e invierno. En las muestras de suelo se determinó análisis físico químico completo, en el forraje se analizó: proteina cruda, fibra detergente neutro, degradabilidad ruminal a las 48 horas, minerales en materia seca. En los sueros de bovinos se determinaron: colesterol, Ca, P, Fe, Mg, proteinas, albúmina y globulinas. Se determinaron diferencias significativas en análisis de suelo por época del año y por localidad. En los análisis foliares, diferencias significativas según época del año. En sueros bovinos, diferencias significativas para hemoglobina, hematocrito, globulinas, entre terneros, novillas y vacas, siendo el último grupo el más crítico. Se sugiere la producción de sal mineralizada que supla deficiencias minerales, suministro contínuo de ésta, mejoramiento en disponibilidad de proteina y energía para mejorar eficiencia productiv

Kinetic study of Arsenic removal in a filter press type electrochemical reactor

El arsénico (As) es un elemento ampliamente distribuido en la naturaleza y de elevada toxicidad para los seres vivos. La presencia de arsénico en el agua subterránea (AN) utilizada para bebida humana o animal es uno de los problemas sanitarios más importantes a nivel mundial. Sin embargo, las poblaciones más afectadas viven en áreas rurales donde la problemática se ve agravada por factores desfavorables de orden socioeconómico, culturales y sanitarios. El AN en diversas áreas de La Comarca Lagunera (México) presenta concentraciones de As superiores a la norma establecida por la Organización Mundial de la Salud (OMS) para agua de bebida (10 mg L-1). Este hecho es muy importante ya que los acuíferos constituyen la principal fuente de abastecimiento a la población. En consecuencia, una amplia gama de tratamientos ha sido desarrollada para remover arsénico de agua modelo (AM) y natural subterránea (AN). Sin embargo, entre ellos, el proceso de electrocoagulación (EC) presenta ventajas importantes sobre los otros procesos debido a que es un método eficiente para el tratamiento de una gran variedad de aguas naturales y residuales. El equipo requerido es compacto y fácil de operar, el proceso evita el uso de reactivos, y por lo tanto no se presentan problemas de neutralización por exceso de químicos evitando que se de una contaminación secundaria. Por esta razón, en este trabajo la remoción de arsénico del agua modelo (AM) y del agua natural subterránea (AN) extraída de la Comarca Lagunera, fue llevada a cabo por el proceso EC. Los experimentos fueron desarrollados inicialmente en un reactor electroquímico filtro prensa tipo batch. De los resultados obtenidos en el reactor, se encontró que la eficiencia de remoción de arsénico se logra a un tiempo de tratamiento inferior de 10 min operado a una densidad de corriente de 15 A m-2 y un flujo volumétrico de 7.64 L min-1.Abstract: Arsenic (As) is a widely distributed element in nature, and is highly toxic for living beings. The presence of arsenic in underground water (GW) used for human or animal consumption is one of the most important sanitation problems at a global level. However, most of the communities that are affected are usually in rural areas, where the problem is worsened by unfavorable socioeconomic, cultural and sanitation factors. The GW in different areas of La Comarca Lagunera (México) presents As concentrations that are above the standard established by World Health Organization (WHO) for drinking water (10 mgL-1). This is an important fact because aquifers are the main supply source for many populated areas. By consequence, a variety of treatment processes have been developed for arsenic removal from model water (MW) and underground water (GW). Nevertheless, among them, the electrocoagulation (EC) process presents important advantages over others due to the low sludge amount produced and the lack of chemical reagents needed, consequently, there is no problem of neutralizing excess chemicals and no possibility of secondary pollution. Moreover, it is an efficient method for the treatment of many natural waters and wastewaters. The equipment required is compact and easy to operate. For this reason, in this work the removal of As from underground water (GW) extracted from La Comarca Lagunera, was performed by the electrocoagulation EC process. Experiments were developed in a batch electrochemical reactor type filter press. According to results obtained in these four reactors, the highest As removal efficiency was achieved at the shortest treatment time (10 min), employing the reactor at a current density value of 15 A m-2 and flow rate of 7.64 L min-1

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.Comment: 16 pages, RevTe

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of the production cross section of prompt j/psi mesons in association with a W (+/-) boson in pp collisions root s=7 TeV with the ATLAS detector

The process pp → W±J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb-1 of p s = 7TeV pp collisions at the LHC, the first observation is made of the production of W± + prompt J/ events in hadronic collisions, using W± → μ and J/ψ → μ+μ-. A yield of 27.4±7.5 -6.5 W± + prompt J/ψ events is observed, with a statistical significance of 5.1. The production rate as a ratio to the inclusive W± boson production rate is measured, and the double parton scattering contribution to the cross section is estimated. Copyright CERN, for the benefit of the ATLAS Collaboration